Optical device, method of manufacturing optical device, quantum computer, and method of controlling quantum computer

Abstract

An optical device(100) includes a substrate(10), a cantilever(20) that extends in a first direction on the substrate(10), includes diamond having a color center(21), and has an end which is a fixed end and another end which is a free end, an optical waveguide(30) that includes a first portion and a second portion that interpose the color center(21) therebetween in a second direction intersecting the first direction, extend in the second direction and are away from the cantilever(20), the first portion andthe second portion including diamonds, and a pair of electrodes(40,41) provided so as to interpose a part of the cantilever(20) located closer to the another end than the color center(21) therebetween.

Description

OPTICAL DEVICE, METHOD OF MANUFACTURING OPTICAL DEVICE, QUANTUM COMPUTER, AND METHOD OF CONTROLLING QUANTUM COMPUTER

[0001] A certain aspect of embodiments described herein relates to an optical device, a method of manufacturing an optical device, a quantum computer, and a method of controlling a quantum computer.

[0002] A quantum computer is being studied as a next-generation computer. For example, the quantum computer using a color center which is a complex defect of a diamond crystal has been proposed (for example, Patent Literatures 1 and 2). In addition, diamond has properties such as high Young's modulus, high hardness, and high thermal conductivity, and excellent corrosion resistance. For this reason, MEMS (Micro Electro Mechanical System) using diamond is also known in order to obtain a high Q-value (for example, Patent Literature 3). In the MEMS, there is known a structure in which electrodes are provided with a beam resonator, which is a cantilever fixed at one end, interposed therebetween (for example, Patent Literature 4).

[0003] Patent Literature 1: U.S. Patent Application Publication No. 2008 / 063339 Patent Literature 2: U.S. Patent Application Publication No. 2020 / 327437 Patent Literature 3: Japanese Laid-Open Patent Publication No. 2019-140547 Patent Literature 4: U.S. Patent No. 7639104

[0004] It is known to construct a quantum computer by combining a plurality of optical devices having color centers. In this case, in order to secure the indistinguishability of photons emitted from the color centers of the plurality of optical devices, it is required to make the light emission frequencies of the color centers of the plurality of optical devices equal to each other. However, since the light emission frequency of the color center varies due to defects and / or distortion around the color center, the light emission frequencies of the color centers of the plurality of optical devices may be different from each other. Therefore, it is desirable to be able to adjust the light emission frequency of the color center.

[0005] In addition, in order to efficiently propagate light for reading irradiated on the color center and light emitted from the color center by the irradiation of the light for reading, it is desired to optically couple the color center and the optical waveguide.

[0006] Accordingly, an object of one aspect is to achieve both adjustment of the light emission frequency of the color center and optical coupling between the color center and the optical waveguide.

[0007] According to an aspect, there is provided an optical device including: a substrate; a cantilever that extends in a first direction on the substrate, includes diamond having a color center, and has an end which is a fixed end and another end which is a free end; an optical waveguide that includes a first portion and a second portion that interpose the color center therebetween in a second direction intersecting the first direction, extend in the second direction and are away from the cantilever, the first portion and the second portion including diamonds; and a pair of electrodes provided so as to interpose a part of the cantilever located closer to the another end than the color center therebetween.

[0008] According to an aspect, there is provided a method of manufacturing an optical device including: forming a cantilever on a substrate, the cantilever extending in a first direction, including diamond having a color center, and having an end which is a fixed end and another end which is a free end; forming an optical waveguide on the substrate, the optical waveguide including a first portion and a second portion that interpose the color center therebetween in a second direction intersecting the first direction, extend in the second direction and are away from the cantilever, the first portion and the second portion including diamonds; and forming a pair of electrodes interposing a part of the cantilever located closer to the another end than the color center therebetween.

[0009] According to an aspect, there is provided a quantum computer including: a plurality of optical devices; wherein each of the plurality of optical devices including: a substrate; a cantilever that extends in a first direction on the substrate, includes diamond having a color center, and has an end which is a fixed end and another end which is a free end; an optical waveguide that includes a first portion and a second portion that interpose the color center therebetween in a second direction intersecting the first direction, extend in the second direction and are away from the cantilever, the first portion and the second portion including diamonds; and a pair of electrodes provided so as to interpose a part of the cantilever located closer to the another end than the color center therebetween.

[0010] According to an aspect, there is provided a method of controlling a quantum computer including a plurality of optical devices each including a substrate, a cantilever that extends in a first direction on the substrate, includes diamond having a color center, and has an end which is a fixed end and another end which is a free end, an optical waveguide that includes a first portion and a second portion that interpose the color center therebetween in a second direction intersecting the first direction, extend in the second direction and are away from the cantilever, the first portion and the second portion including diamonds, and a pair of electrodes provided so as to interpose a part of the cantilever located closer to the another end than the color center therebetween. The method including controlling a voltage applied to the pair of electrodes of each of the plurality of optical devices so that light emission frequencies of color centers of the plurality of optical devices are equal to each other.

[0011] As one aspect, it is possible to achieve both adjustment of the light emission frequency of the color center and optical coupling between the color center and the optical waveguide.

[0012] FIG. 1 is a plan view of an optical device according to a first embodiment.FIG. 2A is a cross-sectional view taken along a line A-A of FIG. 1.FIG. 2B is a cross-sectional view taken along a line B-B of FIG. 1.FIG. 2C is a cross-sectional view taken along a line C-C of FIG. 1.FIG. 3A is a view illustrating a method of manufacturing the optical device according to the first embodiment (part 1).FIG. 3B is a view illustrating a method of manufacturing the optical device according to the first embodiment (part 1).FIG. 3C is a view illustrating a method of manufacturing the optical device according to the first embodiment (part 1).FIG. 3D is a view illustrating a method of manufacturing the optical device according to the first embodiment (part 1).FIG. 4A is a view illustrating a method of manufacturing the optical device according to the first embodiment (part 2).FIG. 4B is a view illustrating a method of manufacturing the optical device according to the first embodiment (part 2).FIG. 4C is a view illustrating a method of manufacturing the optical device according to the first embodiment (part 2).FIG. 4D is a view illustrating a method of manufacturing the optical device according to the first embodiment (part 2).FIG. 5A is a view illustrating a method of manufacturing the optical device according to the first embodiment (part 3).FIG. 5B is a view illustrating a method of manufacturing the optical device according to the first embodiment (part 3).FIG. 5C is a view illustrating a method of manufacturing the optical device according to the first embodiment (part 3).FIG. 5D is a view illustrating a method of manufacturing the optical device according to the first embodiment (part 3).FIG. 6A is a view illustrating a method of manufacturing the optical device according to the first embodiment (part 4).FIG. 6B is a view illustrating a method of manufacturing the optical device according to the first embodiment (part 4).FIG. 6C is a view illustrating a method of manufacturing the optical device according to the first embodiment (part 4).FIG. 6D is a view illustrating a method of manufacturing the optical device according to the first embodiment (part 4).FIG. 7A is a view illustrating a method of manufacturing the optical device according to the first embodiment (part 5).FIG. 7B is a view illustrating a method of manufacturing the optical device according to the first embodiment (part 5).FIG. 7C is a view illustrating a method of manufacturing the optical device according to the first embodiment (part 5).FIG. 7D is a view illustrating a method of manufacturing the optical device according to the first embodiment (part 5).FIG. 8A is a view illustrating a method of manufacturing the optical device according to the first embodiment (part 6).FIG. 8B is a view illustrating a method of manufacturing the optical device according to the first embodiment (part 6).FIG. 8C is a view illustrating a method of manufacturing the optical device according to the first embodiment (part 6).FIG. 8D is a view illustrating a method of manufacturing the optical device according to the first embodiment (part 6).FIG. 9A is a view illustrating a method of manufacturing the optical device according to the first embodiment (part 7).FIG. 9B is a view illustrating a method of manufacturing the optical device according to the first embodiment (part 7).FIG. 9C is a view illustrating a method of manufacturing the optical device according to the first embodiment (part 7).FIG. 9D is a view illustrating a method of manufacturing the optical device according to the first embodiment (part 7).FIG. 10A is a plan view of an optical device according to a second embodiment.FIG. 10B is an enlarged view of a vicinity of a cantilever interposed between a first portion and a second portion of an optical waveguide.FIG. 11A is a cross-sectional view taken along a line A-A in FIG. 10A.FIG. 11B is a cross-sectional view taken along a line B-B in FIG. 10A.FIG. 11C is a cross-sectional view taken along a line C-C in FIG. 10A.FIG. 12A is a plan view of an optical device according to a first modification of the second embodiment.FIG. 12B is an enlarged view of a vicinity of a cantilever interposed between a first portion and a second portion of an optical waveguide.FIG. 13A is a plan view of an optical device according to a second modification of the second embodiment.FIG. 13B is an enlarged view of a vicinity of a cantilever interposed between a first portion and a second portion of an optical waveguide.FIG. 14A is a perspective view of a cantilever used in a simulation.FIG. 14B is a plan view of the cantilever.FIG. 14C is a perspective view of a cantilever used in a simulation.FIG. 14D is a plan view of the cantilever.FIG. 15 is a view illustrating a strain value with respect to an applied voltage in a first simulation.FIG. 16A is a schematic view illustrating a crystal structure of diamond having a color center used in the simulation.FIG. 16B is a view illustrating C transition.FIG. 17 is a view illustrating a light emission frequency with respect to a stress in a second simulation.FIG. 18A is a plan view illustrating a model used in a third simulation.FIG. 18B is an enlarged view of a part of FIG. 18A.FIG. 19 is a view illustrating the magnitude of an electric field amplitude in the third simulation.FIG. 20A is a plan view of an optical device according to a third embodiment.FIG. 20B is an enlarged view of a vicinity of a cantilever interposed between a first portion and a second portion of an optical waveguide.FIG. 21A is a plan view of an optical device according to a fourth embodiment.FIG. 21B is an enlarged view of a vicinity of a cantilever interposed between a first portion and a second portion of an optical waveguide.FIG. 22A is a plan view illustrating a model used in a fourth simulation.FIG. 22B is an enlarged view of a part of FIG. 22A.FIG. 23 is a view illustrating the magnitude of an electric field amplitude in the fourth simulation.FIG. 24 is a block diagram illustrating a quantum computer according to a fifth embodiment.FIG. 25 is a flowchart illustrating an example of adjustment of the light emission frequency of the color center performed by a control unit in the fifth embodiment.

[0013] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings.First Embodiment

[0014] FIG. 1 is a plan view of an optical device 100 according to a first embodiment. FIG. 2A is a cross-sectional view taken along a line A-A in FIG. 1, FIG. 2B is a cross-sectional view taken along a line B-B in FIG. 1, and FIG. 2C is a cross-sectional view taken along a line C-C in FIG. 1. In FIG. 1, for the sake of clarity of the drawing, a support portion 12, a cantilever 20, an optical waveguide 30, projecting portions 14 and 16, and electrodes 40 and 41 are hatched (this hatching applies to the following similar drawings). In FIGs. 1 and 2A to 2C, directions orthogonal to each other on an upper surface of a substrate 10 are defined as an X-axis direction and a Y-axis direction. A thickness direction of the substrate 10 is a Z-axis direction (These directions apply to the following similar drawings). As illustrated in FIGs. 1 and 2A to 2C, the optical device 100 includes the substrate 10, the cantilever 20, the optical waveguide 30, and the electrodes 40 and 41.

[0015] The support portion 12 is provided on the substrate 10 along the periphery of the substrate 10. The substrate 10 is, for example, a sapphire substrate. The support portion 12 is formed of, for example, diamond. The substrate 10 may be a silicon substrate, an alumina substrate, a quartz substrate, a silicon carbide substrate, a diamond substrate, or the like, in addition to a sapphire substrate, and may be an inorganic material substrate or an organic material substrate. The substrate 10 may be formed of a material having a refractive index lower than a refractive index of diamond, for example. The support portion 12 may be formed of, for example, silicon, silicon oxide, silicon nitride, aluminum oxide, or the like, in addition to diamond.

[0016] The cantilever 20 extends in the Y-axis direction and is provided on the substrate 10. One end 22 of the cantilever 20 in the Y-axis direction is a fixed end fixed to the support portion 12, and the other end 23 of the cantilever 20 is a free end. A gap 17 is formed between the cantilever 20 and the substrate 10. The cantilever 20 has a rectangular parallelepiped shape. A length L1 of the cantilever 20 in the Y-axis direction is, for example, 20 μm to 40 μm. A width W1 of the cantilever 20 in the X-axis direction is, for example, 0.1 μm to 0.3 μm. A thickness T1 of the cantilever 20 in the Z-axis direction is, for example, 0.1 μm to 0.3 μm.

[0017] The cantilever 20 is formed of diamond. A color center 21 is formed in the cantilever 20. The color center 21 is formed by ion-implanting atoms into the diamond forming the cantilever 20 and then performing annealing treatment. For example, the color center 21 is formed by ion-implanting tin (Sn) inside the diamond, and is an SnV center which is a complex defect of tin (Sn) substituted for carbon and vacancies (V) in adjacent positions. The color center 21 is formed at the center of the cantilever 20 in the X-axis direction. The color center 21 is formed in the vicinity of an upper surface of the cantilever 20, for example, within a range of 100 nm or less from the upper surface of the cantilever 20. The color center 21 is located closer to the end 22 which is a fixed end of the cantilever 20 than the end 23 which is a free end of the cantilever 20. That is, a distance D1 between the end 22 and the color center 21 is shorter than a distance D2 between the end 23 and the color center 21.

[0018] The optical waveguide 30 includes a first portion 31, a second portion 34, and a region 37 of the cantilever 20 interposed between the first portion 31 and the second portion 34. The color center 21 is formed in the region 37. That is, the first portion 31 and the second portion 34 interpose the location of the color center 21 of the cantilever 20 in the X-axis direction therebetween. The first portion 31 and the second portion 34 extend in the X-axis direction and are provided on the substrate 10. An end 32 of the first portion 31 is provided on the support portion 12, and a remaining portion of the first portion 31 and the substrate 10 are provided with a gap 18 interposed therebetween. An end 35 of the second portion 34 is provided on the support portion 12, and a remaining portion of the second portion 34 and the substrate 10 are provided with the gap 18 interposed therebetween. An edge surface 33 of the first portion 31 on the side opposite to the end 32 faces one side surface of the cantilever 20 in the X-axis direction with a gap therebetween. An edge surface 36 of the second portion 34 on the side opposite to the end 35 faces the other side surface of the cantilever 20 in the X-axis direction with a gap therebetween. Accordingly, the first portion 31 and the second portion 34 are provided so as to interpose the cantilever 20 therebetween in the X-axis direction, and are apart from the cantilever 20. A length G of each of gaps between the cantilever 20, and the first portion 31 and the second portion 34 in the X-axis direction is, for example, 0.01 μm to 0.03 μm.

[0019] The first portion 31 and the second portion 34 are provided with a plurality of through holes 38 arranged in the X-axis direction at intervals. The through holes 38 penetrate the first portion 31 and the second portion 34 and are connected to the gap 18. The through hole 38 has a circular shape in planar view seen from the Z-axis direction, for example. The through holes 38 are provided in the first portion 31 and the second portion 34, so that the first portion 31 and the second portion 34 are formed as a photonic crystal nanoresonator in which the refractive index changes repeatedly at a period of about the wavelength of the light propagating inside. That is, in the first embodiment, the optical waveguide 30 is an optical resonator. The planar shape of the through hole 38 is not limited to the circular shape, but may be an elliptical shape, a rectangular shape, an oval shape, or the like. The sizes of the plurality of through holes 38 may be substantially the same as each other or may be at least partially different. For example, the size of the plurality of through holes 38 may gradually change from the color center 21 toward the ends 32 and 35 opposite to the color center 21.

[0020] The first portion 31 and the second portion 34 are formed of diamond. The first portion 31 and the second portion 34 are formed of diamond, and the region 37 of the cantilever 20 interposed between the first portion 31 and the second portion 34 is also formed of diamond. Therefore, the first portion 31, the second portion 34, and the region 37 function as the optical waveguide 30. Therefore, the laser light for reading irradiated from the end 32 of the first portion 31 toward the color center 21 can be efficiently propagated. The light emitted from the color center 21 by irradiating the laser light for reading can be efficiently extracted from the end portion 35 of the second portion 34. A material having a lower refractive index than the refractive index of diamond forming the first portion 31 and the second portion 34 may be embedded into the through holes 38 formed in the first portion 31 and the second portion 34. For example, silicon oxide may be embedded. In the present embodiment, a description will be given of a case where the color center 21 is irradiated with laser light from the first portion 31 and the light emitted from the color center 21 is extracted from the end portion 35 of the second portion 34 (a resonator of transmission arrangement), but the configuration of the resonator is not limited to this. In another configuration, an effective refractive index of the second portion 34 can be made relatively smaller than that of the first portion 31, for example by adjusting the size of the through holes 38 formed in the second portion 34, so that the light emitted by the color center 21 can be reflected by the second portion 34. In this case, the laser light is irradiated from the first portion 31 to the color center 21, the light emitted from the color center 21 is reflected by the second portion 34, and the reflected light is extracted from the end portion 32 of the first portion 31. Such a configuration is called a resonator of reflective arrangement, and the present disclosure is applicable to such a resonator of reflective arrangement. As a method of making the effective refractive index of the second portion 34 relatively smaller than that of the first portion 31, a method of adjusting the number and density of the through holes 38 in the second portion 34 may be considered in addition to a method of changing the size of the through holes 38.

[0021] The first portion 31 and the second portion 34 are, for example, line-symmetric with respect to a straight line (see a straight line 57 in FIG. 10B) extending in the Y-axis direction through the center of the cantilever 20 in the X-axis direction. Lengths L2 of the first portion 31 and the second portion 34 in the X-axis direction are substantially the same as each other, and are, for example, 9.5 μm to 20 μm. Widths W2 of the first portion 31 and the second portion 34 in the Y-axis direction are substantially the same as each other, and are, for example, 0.1 μm to 0.3 μm. Thicknesses T2 of the first portion 31 and the second portion 34 in the Z-axis direction are substantially the same as each other, and are, for example, 0.1 μm to 0.3 μm. The thickness T2 is substantially the same as the thickness T1 of the cantilever 20.

[0022] The cantilever 20 is provided with a projecting portion 14 and a projecting portion 16 which project from the support portion 12 in the Y-axis direction and interpose the cantilever 20 therebetween in the X-axis direction. The projecting portions 14 and 16 are provided so as to interpose a part of the cantilever 20 in the vicinity of the end 23 therebetween. The projecting portions 14 and 16 are formed of, for example, diamond, but may be formed of, for example, silicon, silicon oxide, silicon nitride, aluminum oxide, or the like in addition to diamond.

[0023] The electrode 40 is provided at least on a surface of the projecting portion 14 facing the cantilever 20. The electrode 41 is provided at least on a surface of the projecting portion 16 facing the cantilever 20. Accordingly, the electrodes 40 and 41 are provided so as to interpose the part of the cantilever 20 in the vicinity of the end 23 therebetween. The electrodes 40 and 41 are formed of a material having a low light absorption in a visible light region, for example, silver (Ag) or tantalum (Ta).

[0024] When a DC voltage is applied between the electrodes 40 and 41, an electrostatic field is formed between the electrodes 40 and 41, and the cantilever 20 is displaced in the direction of an arrow 44 by an electrostatic force. The displacement of the cantilever 20 applies a stress to the color center 21 formed in the cantilever 20. Since an amount of displacement of the cantilever 20 can be controlled by controlling the magnitude of the voltage applied between the electrodes 40 and 41, the magnitude of the stress applied to the color center 21 can be controlled.Manufacturing Method

[0025] FIGs. 3A to 9D are views illustrating a method of manufacturing the optical device 100 according to the first embodiment. FIGs. 3A, 4A, 5A, 6A, 7A, 8A and 9A are plan views illustrating the method of manufacturing the optical device 100. FIGs. 3B, 4B, 5B, 6B, 7B, 8B and 9B, FIGs. 3C, 4C, 5C, 6C, 7C, 8C and 9C, and FIGs. 3D, 4D, 5D, 6D, 7D, 8D and 9D are cross-sectional views taken along lines A-A, B-B, and C-C of FIGs. 3A, 4A, 5A, 6A, 7A, 8A and 9A, respectively.

[0026] As illustrated in FIGs. 3A to 3D, a mask layer 51 having an opening is formed on a single-crystal diamond substrate 50. The diamond substrate 50 is, for example, a diamond (100) substrate or a diamond (001) substrate. The mask layer 51 is formed of, for example, silicon nitride. The diamond substrate 50 is etched by reactive ion etching (RIE) in which oxygen ions are vertically incident using oxygen gas as a reaction gas with the mask layer 51 as a mask. As a result, a recess 52 is formed in the diamond substrate 50.

[0027] As illustrated in FIGs. 4A to 4D, after the mask layer 51 is removed, a surface of the diamond substrate 50 on which the recess 52 is formed is bonded to a temporary substrate 54 through an insulating film 53. The temporary substrate 54 is, for example, a silicon substrate or a sapphire substrate. The insulating film 53 is, for example, a silicon oxide film.

[0028] As illustrated in FIGs. 5A to 5D, the diamond substrate 50 is thinned to a desired thickness by using a processing technique such as mechanical polishing, chemical mechanical polishing, and / or dry etching. For example, the diamond substrate 50 is formed to have a thickness of 1 μm or less.

[0029] As illustrated in FIGs. 6A to 6D, atoms such as tin are ion-implanted into the diamond substrate 50, and then annealing is performed at 1000 °C or higher in a vacuum or inert gas atmosphere. As a result, the color center 21 is formed in the diamond substrate 50. The color center 21 is, for example, an SnV center which is a complex defect of tin (Sn) substituted for carbon and adjacent vacancies (V). As a method of ion implantation, for example, a focused ion beam (FIB) method is used. An acceleration voltage of ion implantation is controlled so that the color center 21 is formed in the vicinity of the surface of the diamond substrate 50. An amount of dose is set to 1010 ions / cm2or less so that the single color center 21 is formed.

[0030] As illustrated in FIGs. 7A to 7D, a mask layer 55 is formed on the diamond substrate 50 to cover regions where the cantilever 20, the optical waveguide 30, the support portion 12, and the projecting portions 14 and 16 are formed and to open the other regions. The mask layer 55 is also provided with openings at positions corresponding to the through holes 38 formed in the optical waveguide 30. The mask layer 55 is formed of, for example, silicon nitride. Thereafter, the diamond substrate 50 is etched by reactive ion etching in which oxygen ions are vertically incident, using oxygen gas as a reaction gas, with the mask layer 55 as a mask.

[0031] As illustrated in FIGs. 8A to 8D, the mask layer 55 is removed and the diamond substrate 50 is peeled from the temporary substrate 54.

[0032] As illustrated in FIGs. 9A to 9D, the diamond substrate 50 is bonded to the substrate 10. The diamond substrate 50 and the substrate 10 are bonded by a direct bonding method such as surface activated bonding at room temperature. The diamond substrate 50 and the substrate 10 may be bonded to each other with an adhesive or the like. The substrate 10 is, for example, a sapphire c-plane substrate. Thus, the cantilever 20, the optical waveguide 30 including the first portion 31 and the second portion 34, the support portion 12, and the projecting portions 14 and 16 are formed by the diamond substrate 50. The gap 17 is formed between the cantilever 20 and the substrate 10, and the gap 18 is formed between the substrate 10, and the first portion 31 and the second portion 34. Thereafter, the electrodes 40 and 41 are formed by, for example, an oblique evaporation method and a lift-off method. By forming the electrodes 40 and 41 made of silver or tantalum, the adhesion of the electrodes 40 and 41 to the projecting portions 14 and 16 can be enhanced.

[0033] According to the first embodiment, as illustrated in FIGs. 1 and 2A to 2C, the cantilever 20 including diamond having the color center 21 and having one end 22 as a fixed end and the other end 23 as a free end is provided on the substrate 10. The electrodes 40 and 41 are provided so as to interpose the part of the cantilever 20 positioned closer to the end 23 than the color center 21 therebetween. When the voltage is applied between the electrodes 40 and 41, the cantilever 20 is displaced in the direction of the arrow 44. When the cantilever 20 is displaced in the direction of the arrow 44, the stress is applied to the color center 21 formed in the cantilever 20. Since the amount of displacement of the cantilever 20 can be controlled by controlling the magnitude of the voltage applied between the electrodes 40 and 41, the magnitude of the stress applied to the color center 21 can be controlled. Since the light emission frequency of the color center 21 changes depending on the magnitude of the stress applied to the color center 21, the light emission frequency of the color center 21 can be adjusted by controlling the magnitude of the voltage applied between the electrodes 40 and 41. The optical waveguide 30 is provided which has the first portion 31 and the second portion 34 that include diamond and extend in the X-axis direction, respectively, and interpose the color center 21 therebetween in the X-axis direction. This improves the optical coupling between the color center 21 and the optical waveguide 30. The first portion 31 and the second portion 34 are provided away from the cantilever 20. Therefore, even if the cantilever 20 is displaced, the influence on the first portion 31 and the second portion 34 is small, and the change in the characteristic of the optical waveguide 30 is suppressed. As described above, according to the first embodiment, both the adjustment of the light emission frequency of the color center 21 and the optical coupling between the color center 21 and the optical waveguide 30 can be achieved.

[0034] In the first embodiment, as illustrated in FIG. 2A, the distance D1 between the end 22, which is a fixed end, and the color center 21 is shorter than the distance D2 between the end 23, which is a free end, and the color center 21. This makes it easy for a large stress to be applied to the color center 21 when the voltage is applied between the electrodes 40 and 41 to displace the cantilever 20. In view of applying the large stress to the color center 21, the distance D1 is preferably equal to or less than 1 / 3 of the distance D2, more preferably equal to or less than 1 / 4 of the distance D2, and still more preferably equal to or less than 1 / 5 of the distance D2.Second Embodiment

[0035] FIG. 10A is a plan view of an optical device 200 according to a second embodiment, and FIG. 10B is an enlarged view of the vicinity of a cantilever 20a interposed between the first portion 31 and the second portion 34 of the optical waveguide 30. FIG. 11A is a cross-sectional view taken along the line A-A in FIG. 10A, FIG. 11B is a cross-sectional view taken along the line B-B in FIG. 10A, and FIG. 11C is a cross-sectional view taken along the line C-C in FIG. 10A. As illustrated in FIGs. 10A, 10B, and 11A to 11C, in the second embodiment, the cantilever 20a is provided with recesses 26 in respective side surfaces 24 and 25 facing each other in the X-axis direction in the region 37 interposed between the first portion 31 and the second portion 34. The recess 26 formed in the side surface 24 and the recess 26 formed in the side surface 25 are symmetrical with respect to the straight line 57 extending in the Y-axis direction through the center of the cantilever 20a in the X-axis direction. Recesses 39 are formed in the edge surfaces of the first portion 31 and the second portion 34. Each of the recesses 26 and 39 has, for example, an arc shape in planar view seen from the Z-axis direction. The recess 26 and the recess 39 face each other, and a gap 58 is formed therebetween. The gaps 58 are provided in the plurality of through holes 38 provided in the first portion 31 and the second portion 34, and are arranged in the X-axis direction at intervals. The gaps 58 are arranged and spaced apart in the X-axis direction from the plurality of through holes 38 provided in the first portion 31 and the second portion and 34. Therefore, the gaps 58 corresponding to the through holes 38 are formed between the first portion 31 and the cantilever 20a and between the second portion 34 and the cantilever 20a.

[0036] The recesses 26 in the cantilever 20a make a width W3 of the cantilever 20a at the location where the color center 21 is located narrower than a width W1 of the cantilever 20a at the ends 22 and 23. For example, the color center 21 is interposed between the deepest portions of the recesses 26, whereby the width W3 is the narrowest. Metal films 42 and 43 facing the electrodes 40 and 41 are provided on the side surfaces 24 and 25 of the cantilever 20a. The other configurations are the same as those of the first embodiment, and therefore, the description thereof is omitted.Modifications

[0037] FIG. 12A is a plan view of an optical device 210 according to a first modification of the second embodiment, and FIG. 12B is an enlarged view of the vicinity of a cantilever 20b interposed between the first portion 31 and the second portion 34 of the optical waveguide 30. As illustrated in FIGs. 12A and 12B, in the first modification of the second embodiment, the shapes of the recesses 26a provided in the side surfaces 24 and 25 of the cantilever 20b are different from the shapes of the recesses 26 in the second embodiment. The recesses 26a has shapes in which rectangular portions 27 having rectangular shapes provided on the side surfaces 24 and 25 of the cantilever 20b and arc-shaped arc portions 29 provided on the bottom surfaces of the rectangular portions 27 in the X-axis direction are combined in planar view seen from the Z-axis direction. The recess 26a formed in the side surface 24 and the recess 26a formed in the side surface 25 are symmetrical with respect to the straight line 57 extending in the Y-axis direction through the center of the cantilever 20b in the X-axis direction, as in the second embodiment. The arc portion 29 and the recess 39 face each other, and the gap 58 is formed therebetween. The other configurations are the same as those of the second embodiment, and therefore the description thereof is omitted.

[0038] FIG. 13A is a plan view of an optical device 220 according to a second modification of the second embodiment, and FIG. 13B is an enlarged view of the vicinity of a cantilever 20c interposed between the first portion 31 and the second portion 34 of the optical waveguide 30. As illustrated in FIGs. 13A and 13B, in the second modification of the second embodiment, the shapes of the recesses 26b provided in the side surfaces 24 and 25 of the cantilever 20c are V-shapes in planar view seen from the Z-axis direction. The recess 26b formed in the side surface 24 and the recess 26b formed in the side surface 25 are symmetrical with respect to the straight line 57 extending in the Y-axis direction through the center of the cantilever 20c in the X-axis direction, as in the second embodiment. The recess 26b and the recess 39 face each other, and the gap 58 is formed therebetween. The other configurations are the same as those of the second embodiment, and therefore the description thereof is omitted.First Simulation

[0039] For the cantilevers 20a and 20c in the second embodiment and the second modification of the second embodiment, the strain generated at the color center 21 was simulated by a finite element method when the voltage applied to the electrodes 40 and 41 was changed. FIGs. 14A and 14C are perspective views of the cantilevers 20a and 20c used in the simulation, and FIGs. 14B and 14D are plan views. The simulation conditions are as follows. Common simulation conditions Materials of Cantilevers 20a and 20c: Diamond (Young's modulus: 1000 GPa, Poisson's ratio: 0.1, Density: 3.515 g / cm3) Lengths L of Cantilevers 20a and 20c: 20 μm Widths W1 of Cantilevers 20a and 20c: 200 nm Thicknesses T of Cantilevers 20a and 20c: 200 nm Distances D from End 22 to Color Center 21: 5 μm Forming Position of Color Center 21: 50 nm from Upper Surfaces of Cantilevers 20a and 20c Simulation Conditions of Second Embodiment Depth a of Recess 26: 50 nm Length b of Recess 26: 100 nm Width W2: 100nm Simulation Conditions of Second Modification of Second Embodiment Depth c of Recess 26: 50 nm Width d of Recess 26b: 100 nm Width W2: 100 μm

[0040] FIG. 15 is a view illustrating the strain value with respect to the applied voltage in the first simulation. In FIG. 15, a horizontal axis represents the voltage applied between the electrodes 40 and 41 in V unit, and a vertical axis represents strain values generated at the positions where the color centers 21 of the cantilevers 20a and 20c are provided. A negative value of the strain value indicates a case where the cantilever has shrunk. As illustrated in FIG. 15, in both of the second embodiment and the second modification of the second embodiment, the strain varied depending on the magnitude of the applied voltage, and an absolute value of the strain increased as the applied voltage increased. The absolute value of the strain of the second modification of the second embodiment was larger than that of the second embodiment. For example, when a voltage of 70 V was applied, the strain value was about - 2.2 × 10-4in the second embodiment, while the strain value was about - 3.1 × 10-4in the second modification of the second embodiment. From this, it is understood that the distortion can be effectively generated in the cantilever by forming the recesses of V-shapes in the cantilever.Second Simulation

[0041] A simulation was performed on the relationship between the magnitude of the stress applied to the color center 21 and the light emission frequency of the color center 21. FIG. 16A is a schematic view illustrating a crystal structure of diamond having the color center 21 used in the simulation. As illustrated in FIG. 16A, the color center 21 is formed of an SnV center which is a complex defect of a tin atom 86 substituted for a carbon atom 85 and adjacent vacancies 87 in a diamond in which the carbon atoms 85 are covalently bonded. The simulation was performed by calculating the change in the light emission frequency of the color center 21 when a stress was applied in a

[0100] direction of diamond with reference to an electronic state Hamiltonian of the color center composed of a group IV element and the vacancies. Applying the stress in the

[0100] direction of diamond corresponds to applying the stress to the color center 21 from a direction of an arrow 89 perpendicular to a defect axis 88 when a direction in which the tin atom 86 and the vacancies 87 are aligned is defined as the defect axis 88.

[0042] FIG. 16B is a diagram illustrating C transition. As illustrated in FIG. 16B, the color center such as an SnV center has two branched ground levels GUB(UB: Upper Branch) and GLB(LB: Lower Branch), and an excitation level EUBat a zero magnetic field. The ground levels GUBand GLBand the excited level EUBare spin-split by an external magnetic field, thereby forming four spin levels, respectively. Assuming that two levels are selected in order from the lowest intrinsic energy of the ground levels and the superposition state thereof is used as a qubit, the optical response (C transition) between the two levels constituting the qubit and the two levels of the excited levels EUBis used for reading out the state. The two C transitions include C1 transition and C2 transition.

[0043] FIG. 17 is a graph illustrating the light emission frequency with respect to the stress in a second simulation. In FIG. 17, a horizontal axis represents the stress applied to the color center 21 in GPa unit, and a vertical axis represents the emission frequency in Hz unit. As illustrated in FIG. 17, it is understood that a stress of about 0.8 GPa needs to be applied to the color center 21 in order to shift the light emission frequency from 3.03898 × 1015Hz to 3.03908 × 1015Hz by 100 GHz in the C1 transition.

[0044] It is understood from FIG. 17 that the light emission frequency of the color center 21 can be adjusted by controlling the stress applied to the color center 21. In the first and second embodiments and the modification thereof, the stress is applied to the color center 21 by applying a voltage between the electrodes 40 and 41 to displace the cantilever. Since an amount of displacement of the cantilever can be controlled by controlling the voltage applied between the electrode 40 and the electrode 41, the distortion generated in the color center 21 can be controlled as illustrated in FIG. 15. This makes it possible to control the stress applied to the color center 21. Therefore, the light emission frequency of the color center 21 can be adjusted by controlling the voltage applied between the electrodes 40 and 41. For example, applying a stress of about 0.8 GPa to the color center 21 can be realized by setting the strain value generated in the color center 21 to 10-4to 10-3.Third Simulation

[0045] FIG. 18A is a plan view illustrating a model used in a third simulation, and FIG. 18B is an enlarged view of a part of FIG. 18A. As illustrated in FIGs. 18A and 18B, in the simulation, it was assumed that a point light source 90 assuming the SnV center was provided in the region 37 of the cantilever 20a interposed between the first portion 31 and the second portion 34. Then, an electric field intensity distribution of the light emitted from the point light source 90 was calculated by a finite difference time domain method. The simulation conditions are as follows. Materials of Cantilever 20a, First portion 31, and Second portion 34: Diamond Light Emission wavelength of Point light source 90: 620 nm Length L1 of Cantilever 20a: 1.84 μm Width W1 of Cantilever 20a: 200 nm Thickness of Cantilever 20a: 145 nm Length L2 of Optical Waveguide 30: 4.67 μm Width W2 of Optical Waveguide 30: 277 nm Thickness of Optical Waveguide 30: 239 nm Through hole 38: Diameter gradually changes in range of 82 nm to 96 nm from Color center 21 side toward side opposite to Color center 21 Ratio of Pitch of Through hole 38 to Diameter of Through hole 38: 0.28 Gap G between Cantilever 20a, and First portion 31 and Second portion 34: 20 nm

[0046] FIG. 19 is a view illustrating the magnitude of an electric field amplitude in the third simulation. In FIG. 19, the relative magnitude of the electric field amplitude is illustrated by contour lines. As illustrated in FIG. 19, the electric fields generated in the first portion 31 and the second portion 34 were small in inclination with respect to the Y-axis direction. The electric field generated in the first portion 31 and the electric field generated in the second portion 34 represent intensity distributions with good symmetry with respect to the cantilever 20a. From this result, it can be said that the optical waveguide 30 including the first portion 31, the second portion 34, and the region 37 functions as an optical resonator in which the propagation loss of light is reduced.

[0047] In the second embodiment and the modifications thereof, as illustrated in FIGs. 10B, 12B and 13B, the widths W3 of the cantilevers 20a to 20c at the position of the color center 21 are smaller than the widths W1 at the ends 22 and 23. Thus, a large stress is easily applied to the color center 21 by applying the voltage between the electrodes 40 and 41. Therefore, the adjustment range of the light emission frequency of the color center 21 is increased.

[0048] In the second embodiment and the modifications thereof, the cantilevers 20a to 20c are provided with the recesses 26 to 26b (first recesses) on the side surfaces 24 and 25 facing each other in the X-axis direction, so that the width W3 is smaller than the width W1. This makes it easy to obtain a structure in which the large stress is easily applied to the color center 21 by applying the voltage between the electrodes 40 and 41.

[0049] In the second embodiment and the modification thereof, the color center 21 is interposed between the deepest portions of the recesses 26 to 26b provided in the side surfaces 24 and 25 of the cantilevers 20a to 20c, so that the width W3 at the position of the color center 21 is the narrowest. This makes it easy for the large stress to be applied to the color center 21 by applying the voltage between the electrodes 40 and 41.

[0050] In the second modification of the second embodiment, the recess 26b has a V-shape in planar view as illustrated in FIG. 13B. As a result, as illustrated in FIG. 15, the large stress is easily applied to the color center 21 by applying the voltage between the electrodes 40 and 41.

[0051] According to the second embodiment and the modifications thereof, the recesses 26 to 26b are symmetrical with respect to the straight line 57 extending in the Y-axis direction through the center of the cantilevers 20a to 20c in the X-axis direction. This allows the region 37 of the cantilevers 20a to 20c interposed between the first portion 31 and the second portion 34 to have a symmetrical structure, so that the first portion 31, the second portion 34 and the region 37 can function well as the optical waveguide 30.

[0052] In the second embodiment and the modification thereof, as illustrated in FIGs. 10B, 12B and 13B, the first portion 31 and the second portion 34 of the optical waveguide 30 have the recesses 39 (second recess) facing the recesses 26a to 26c on the edge surface facing the cantilevers 20a to 20c. The recesses 26 to 26c and the recesses 39 are provided between the first portion 31 and the second portion 34 and the cantilevers 20a to 20c, so that the gaps 58, which correspond to the through holes 38 and are aligned with the through holes 38 with spacings in the X-axis direction in planar view, are formed. This allows the whole of the first portion 31, the second portion 34, and the region 37 of the cantilevers 20a to 20c to function as a photonic crystal nanoresonator.Third Embodiment

[0053] FIG. 20A is a plan view of an optical device 300 according to a third embodiment, and FIG. 20B is an enlarged view of a vicinity of the cantilever 20a interposed between the first portion 31 and the second portion 34 of an optical waveguide 30a. As illustrated in FIGs. 20Aa and 20B, in the third embodiment, the through hole 38 and the recess 39 are not provided in the optical waveguide 30a. The other configurations are the same as those of the second embodiment, and therefore, the description thereof is omitted.

[0054] In the first and second embodiments and the modifications thereof, the optical waveguide 30 is the optical resonator provided with the through holes 38, but the optical waveguide 30a may be an optical waveguide provided with no through hole 38 as in the third embodiment.Fourth Embodiment

[0055] FIG. 21A is a plan view of an optical device according to a fourth embodiment 400, and FIG. 21B is an enlarged view of a vicinity of a cantilever 20d interposed between the first portion 31 and the second portion 34 of the optical waveguide 30a. As illustrated in FIGs. 21A and 21B, in the fourth embodiment, the optical waveguide 30a is not provided with the through hole 38 and the recess 39, but the cantilever 20d is provided with a plurality of through holes 28. The plurality of through holes 28 are provided symmetrically in the Y-axis direction with respect to the color center 21, for example. The other configurations are the same as those of the second embodiment, and therefore, the description thereof is omitted. The through hole 28 is not limited to a circular shape in planar view, but may be an elliptical shape, a rectangular shape, an oval shape, or the like, as in the case of the through hole 38. The sizes of the plurality of through holes 28 may be substantially the same as each other or may be at least partially different. For example, the sizes of the through holes 28 may gradually change from the color center 21 side to the side opposite to the color center 21.Fourth Simulation

[0056] FIG. 22A is a plan view illustrating a model used in a fourth simulation, and FIG. 22B is an enlarged view of a part of FIG. 22A. As illustrated in FIGs. 22A and 22B, in the simulation, it was assumed that the point light source 90 assuming the SnV center was provided in the region 37 of the cantilever 20d interposed between the first portion 31 and the second portion 34. Then, an electric field intensity distribution of the light emitted from the point light source 90 was calculated by the finite difference time domain method. The simulation conditions are as follows. Materials of Cantilever 20a, First portion 31, and Second portion 34: Diamond Light Emission wavelength of Point light source 90: 620 nm Length L1 of Cantilever 20d: 4.67 μm Width W1 of Cantilever 20d: 277 nm Thickness of Cantilever 20d: 145 nm Through hole 28: Diameter gradually changes in range of 82 nm to 96 nm from Color center 21 side to side opposite to Color center 21 Ratio of Pitch of Through hole 28 to Diameter of Through hole 28: 0.28 Length L2 of Optical Waveguide 30a: 1.84 μm Width W2 of Optical Waveguide 30a: 100 nm Thickness of Optical Waveguide 30a: 239 nm Gap G between Cantilever 20d, and First portion 31 and Second portion 34: 14 nm

[0057] FIG. 23 is a view illustrating the magnitude of an electric field amplitude in the fourth simulation. In FIG. 23, the relative magnitude of the electric field amplitude is illustrated by contour lines. As illustrated in FIG. 23, the electric field generated in the cantilever 20d has a small inclination with respect to the X-axis direction. The electric field generated in the cantilever 20d represents an intensity distribution with good symmetry with respect to the optical waveguide 30 including the first portion 31 and the second portion 34. From this result, it is understood that Purcell effect can be obtained by providing the through holes 28 in the cantilever 20d.

[0058] According to the fourth embodiment, as illustrated in FIGs. 21A and 21B, the cantilever 20d has the plurality of through holes 28 arranged in the Y-axis direction with gaps therebetween in planar view. This provides the Purcell effect, and enhances the light emission rate of the light emitted from the color center 21, thereby improving the ease of light emission per unit time.

[0059] Further, in the first embodiment, the second embodiment and the modifications thereof, the third embodiment and the fourth embodiment, a case where the color center 21 is the SnV center which is the complex defect of tin (Sn) and vacancies (V) is represented as an example. However, the present disclosure is not limited to this case. The color center 21 may be a complex defect of at least one of nitrogen (N), silicon (Si), germanium (Ge), tin (Sn), and lead (Pb) atoms and vacancies.

[0060] In the first embodiment, the second embodiment and the modifications thereof, the third embodiment, and the fourth embodiment, the voltage is applied between the electrodes 40 and 41, whereby the stress having a component in the direction of the arrow 89 perpendicular to the defect axis 88 of the color center 21 is applied to the color center 21, as illustrated in FIG. 16A. This makes it possible to favorably adjust the light emission frequency of the color center 21 corresponding to a transition frequency between the ground level and the excited level.

[0061] In the first embodiment, the second embodiment and the modifications thereof, the third embodiment and the fourth embodiment, the cantilevers 20 to 20d are displaced in the planar direction of the substrate 10 by the electrostatic field generated when the voltage is applied between the electrodes 40 and 41. This makes it possible to control the amount of displacement of the cantilevers 20 to 20d with high accuracy.Fifth Embodiment

[0062] FIG. 24 is a block diagram illustrating a quantum computer 500 according to a fifth embodiment. As illustrated in FIG. 24, the quantum computer 500 includes a control unit 60, drive units 61, optical switches 62, single photon detectors 63, a beam splitter 64, a comparator 65, AD converters 66, and the optical devices 100 according to the first embodiment. The control unit 60 is, for example, a PC (Personal Computer). The control unit 60 outputs control signals to the drive units 61. The control signals output from the control unit 60 are input to the drive units 61 via the AD converters 66. The components other than the control unit 60 and the AD converter 66 are used in an environment of a very low temperature (for example, 4 Kelvin or less).

[0063] The quantum computer 500 includes a plurality of optical devices 100, and the drive unit 61 is provided for each of the plurality of optical devices 100. The drive unit 61 controls the magnetic field applied to the optical device 100, the microwave input to the optical device 100, the laser light incident on the optical waveguide 30 of the optical device 100, and the voltage applied between the electrodes 40 and 41 of the optical device 100 in accordance with the control signal from the control unit 60. The magnetic field is used to form the state of the color center 21 where the quantum operation is performed. The microwaves are used to control the state of the color center 21. The laser light is used to read out the state of the color center 21. The voltage applied between the electrodes 40 and 41 is used to adjust the light emission frequency of the color center 21 by displacing the cantilever 20 and applying the stress to the color center 21.

[0064] The plurality of optical devices 100 are divided into a first group 67 connected in parallel and a second group 68 connected in parallel. The optical devices 100 of the first group 67 and the optical devices 100 of the second group 68 are connected to one beam splitter 64 through separate optical switches 62. The optical devices 100 of the first group 67 and the optical devices 100 of the second group 68 are connected to separate single photon detectors 63 through the optical switches 62. A path along which photons generated from each of the plurality of optical devices 100 proceed is switched by the optical switch 62 between a path along which the photons are guided directly to the single photon detector 63 and a path along which the photons are guided to the single photon detector 63 via the beam splitter 64.

[0065] The path along which the photons are directed to the single photon detector 63 is used when reading the state of a single qubit. The path along which the photons are guided to the single photon detector 63 via the beam splitter 64 is used when operating on the optical devices 100 having the same optical path length from the beam splitter 64 during the operation of entanglement between the color centers 21 corresponding to the multi-gate operation.

[0066] The comparator 65 compares the single photons detected by the single photon detector 63 after being split by the beam splitter 64. For example, the comparator 65 compares which single photon detector 63 detects the photons and in what order. The output from the comparator 65 is input to the control unit 60. The result of the analysis of the output from the comparator 65 by the control unit 60 corresponds to the result of the operation by the quantum computer.

[0067] In the fifth embodiment, the case where the optical device 100 of the first embodiment is provided is described as an example, but the optical device of the second embodiment and the modifications thereof, the third embodiment, or the fourth embodiment may be provided.

[0068] FIG. 25 is a flowchart illustrating an example of adjustment of the light emission frequency of the color center 21 performed by the control unit 60 in the fifth embodiment. As illustrated in FIG. 25, the control unit 60 determines whether the light emission frequencies of the color centers 21 of the plurality of optical devices 100 are equal to each other (step S10). Whether the light emission frequencies of the color centers 21 are equal to each other is determined by monitoring, for example, quantum interference between photons. For example, when photons are made incident on the beam splitter 64 from each of the two optical switches 62 and the photons are detected only by one of the single photon detectors 63, it is determined that the light emission frequencies are equal to each other.

[0069] When the light emission frequencies of the color centers 21 are equal to each other (step S10: Yes), the present flowchart is ended. On the other hand, when the light emission frequencies of the color centers 21 are not equal to each other (step S10: No), the control unit 60 outputs a control signal to the drive unit 61 to apply the voltage between the electrode 40 and the electrode 41 of at least one optical device 100 in the plurality of optical devices 100 (step S12).

[0070] Next, the control unit 60 determines whether the light emission frequencies of the color centers 21 are equal to each other (step S14). When the light emission frequencies are equal to each other (step S14: Yes), the present flowchart is ended. When the light emission frequencies of the color centers 21 are not yet equal to each other (step S14: No), the magnitude of the voltage applied between the electrodes 40 and 41 is changed (step S16). The steps S14 and S16 are repeated until the light emission frequencies of the color centers 21 are equal to each other.

[0071] As described above, the quantum computer 500 according to the fifth embodiment includes the plurality of optical devices 100 according to the first embodiment. Therefore, by controlling the magnitude of the voltage applied between the electrodes 40 and 41, the light emission frequency of the color center 21 can be adjusted, and the light emission frequencies of the color centers 21 of the plurality of optical devices 100 can be equal to each other.

[0072] In the fifth embodiment, as illustrated in FIG. 25, the control unit 60 controls the voltages applied between the electrodes 40 and 41 of the plurality of optical devices 100 so that the light emission frequencies of the color centers 21 of the respective optical devices 100 are equal to each other. This ensures the indistinguishability of the photons emitted by the color centers 21 of the plurality of respective optical devices 100.

[0073] Although the embodiments of the present disclosure have been described in detail, the present disclosure is not limited to the specific embodiments, but various variations and changes are possible within the scope of the gist of the present disclosure as described in the claims.

[0074] 10…substrate, 12…support portion, 14…projecting portion, 16…projecting portion, 17…gap, 18…gap, 20, 20a, 20b, 20c, 20d…cantilever, 21…color center, 22…end, 23…end, 24…side surface, 25…side surface, 26, 26a, 26b… recess, 27…rectangular portion, 28…through hole, 29…arc portion, 30, 30a…optical waveguide, 31…first portion, 32…end, 33…edge surface, 34…second portion, 35...end, 36...edge surface, 37…region, 38…through hole, 39…recess, 40…electrode, 41…electrode, 42…metal film, 43... metal film, 50…diamond substrate, 51…mask layer, 52…recess, 53…insulating film, 54...temporary substrate, 55…mask layer, 57...straight line, 58…gap, 60…control unit, 61…drive portion, 62…optical switch, 63…single photon detector, 64...beam splitter, 65…comparator, 66...AD converter, 67... first group, 68… second group, 85…carbon atom, 86…tin atom, 87. vacancy, 88…defect axis, 90…point light source, 100, 200, 210, 220, 300, 400…optical device, 500…quantum computer

Claims

1. An optical device comprising: a substrate; a cantilever that extends in a first direction on the substrate, includes diamond having a color center, and has an end which is a fixed end and another end which is a free end; an optical waveguide that includes a first portion and a second portion that interpose the color center therebetween in a second direction intersecting the first direction, extend in the second direction and are away from the cantilever, the first portion and the second portion including diamonds; and a pair of electrodes provided so as to interpose a part of the cantilever located closer to the another end than the color center therebetween.

2. The optical device according to claim 1, wherein the cantilever has a width in the second direction at a position of the color center smaller than widths in the second direction at the end and the another end.

3. The optical device according to claim 2, wherein first recesses are provided on side surfaces of the cantilever facing each other in the second direction, respectively, whereby the width in the second direction at the position of the color center is smaller than the widths in the second direction at the end and the another end.

4. The optical device according to claim 3, wherein the cantilever has a narrowest width in the second direction at the position of the color center by interposing the color center between deepest portions of the first recesses.

5. The optical device according to claim 3 or 4, wherein each of the first recesses has a V-shape in planar view.

6. The optical device according to claim 3 or 4, wherein each of the first recesses has an arc shape in planar view.

7. The optical device according to claim 3 or 4, wherein the first recesses provided on the side surfaces of the cantilever facing each other, respectively, are symmetrical with respect to a straight line extending in the first direction through a center of the cantilever in the second direction.

8. The optical device according to claim 3 or 4, wherein the first portion and the second portion have a plurality of through holes which penetrate the first portion and the second portion and are arranged in the second direction with gaps therebetween in planar view, and second recesses which are provided on edge surfaces facing the cantilever so as to face the first recesses.

9. The optical device according to claim 1 or 2, wherein the cantilever has a plurality of through holes arranged in the first direction with gaps therebetween across the color center in planar view.

10. The optical device according to claim 1 or 2, wherein a distance between the end and the color center is shorter than a distance between the another end and the color center.

11. The optical device according to claim 1 or 2, wherein the color center is applied with a stress having a component in a direction perpendicular to a defect axis of the color center by applying a voltage to the pair of electrodes.

12. The optical device according to claim 1 or 2, wherein the cantilever is displaced in a plane direction of the substrate by an electrostatic field generated when a voltage is applied to the pair of electrodes.

13. The optical device according to claim 1 or 2, further comprising: metal films provided on side surfaces of the cantilever facing the pair of electrodes.

14. A method of manufacturing an optical device comprising: forming a cantilever on a substrate, the cantilever extending in a first direction, including diamond having a color center, and having an end which is a fixed end and another end which is a free end; forming an optical waveguide on the substrate, the optical waveguide including a first portion and a second portion that interpose the color center therebetween in a second direction intersecting the first direction, extend in the second direction and are away from the cantilever, the first portion and the second portion including diamonds; and forming a pair of electrodes interposing a part of the cantilever located closer to the another end than the color center therebetween.

15. A quantum computer comprising: a plurality of optical devices; wherein each of the plurality of optical devices including: a substrate; a cantilever that extends in a first direction on the substrate, includes diamond having a color center, and has an end which is a fixed end and another end which is a free end; an optical waveguide that includes a first portion and a second portion that interpose the color center therebetween in a second direction intersecting the first direction, extend in the second direction and are away from the cantilever, the first portion and the second portion including diamonds; and a pair of electrodes provided so as to interpose a part of the cantilever located closer to the another end than the color center therebetween.

16. A method of controlling a quantum computer comprising a plurality of optical devices each including a substrate, a cantilever that extends in a first direction on the substrate, includes diamond having a color center, and has an end which is a fixed end and another end which is a free end, an optical waveguide that includes a first portion and a second portion that interpose the color center therebetween in a second direction intersecting the first direction, extend in the second direction and are away from the cantilever, the first portion and the second portion including diamonds, and a pair of electrodes provided so as to interpose a part of the cantilever located closer to the another end than the color center therebetween, the method comprising: controlling a voltage applied to the pair of electrodes of each of the plurality of optical devices so that light emission frequencies of color centers of the plurality of optical devices are equal to each other.

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